One of the main purposes of basic training is to see how recruits handle stresses which are intended to replace the real stresses of combat. This is why drill instructors scream and act like they hate recruits. If your fiance is unable to handle being screamed at up close and personal, it would be the responsible thing for them to disqualify him, but it's still possible they will make the decision to allow him to be recycled and placed with another unit.